An efficient way of high-contrast, quasi-3D cellular imaging: Off-axis illumination

An imaging system enabling a convenient visualisation of cells and other small objects is presented. It represents an adaptation of the optical microscope condenser. accommodating a built-in edge (relief) diaphragm brought close to the condenser iris diaphragm and enabling high-contrast pseudo-relief (quasi-3D) imaging. The device broadens the family of available apparatus based oil the off-axis (or anaxial. asymmetric. inclined, oblique, schlieren-type, sideband) illumination. The simplicity of the design makes the condenser a user-friendly, dedicated device delivering high-contrast quasi-3D images of phase objects. Those are nearly invisible under the ordinary (axial) illumination. The phase contrast microscopy commonly used in visualisation of phase objects does not deliver the quasi-3D effect and introduces a disturbing 'halo' effect around the edges. The performance of the device presented here is demonstrated on living cells and tissue replicas. High-contrast quasi-3D images of cell-free preparations of biological origin (paper fibres and microcrystals) are shown as well. (c) 2006 Elsevier B.V. All rights reserved.